How to log line number of coder in boost log 2.0?

Question

Can I use LineID attribute for this? I hope I could use sink::set_formatter to do this instead of using

__LINE__

and

__FILE__

in each log statement.

Answer 1

The LineID attribute is a sequential number that is incremented for each logging message. So you can't use that.

You can use attributes to log the line numbers etc. This allows you flexible formatting using the format string, whereas using Chris' answer your format is fixed.

Register global attributes in your logging initialization function:

using namespace boost::log;
core::get()->add_global_attribute("Line", attributes::mutable_constant<int>(5));
core::get()->add_global_attribute("File", attributes::mutable_constant<std::string>(""));
core::get()->add_global_attribute("Function", attributes::mutable_constant<std::string>(""));

Setting these attributes in your logging macro:

#define logInfo(methodname, message) do {                           \
    LOG_LOCATION;                                                       \
    BOOST_LOG_SEV(_log, boost::log::trivial::severity_level::info) << message; \
  } while (false)

#define LOG_LOCATION                            \
  boost::log::attribute_cast<boost::log::attributes::mutable_constant<int>>(boost::log::core::get()->get_global_attributes()["Line"]).set(__LINE__); \
  boost::log::attribute_cast<boost::log::attributes::mutable_constant<std::string>>(boost::log::core::get()->get_global_attributes()["File"]).set(__FILE__); \
  boost::log::attribute_cast<boost::log::attributes::mutable_constant<std::string>>(boost::log::core::get()->get_global_attributes()["Function"]).set(__func__);

Not exactly beautiful, but it works and it was a long way for me. It's a pity boost doesn't offer this feature out of the box.

The do {... } while(false) is to make the macro semantically neutral.

Answer 2

The solution shown by Chris works, but if you want to customize the format or choose which information appears in each sink, you need to use mutable constant attributes:

   logging::core::get()->add_global_attribute("File", attrs::mutable_constant<std::string>(""));
   logging::core::get()->add_global_attribute("Line", attrs::mutable_constant<int>(0));

Then, you make a custom macro that includes these new attributes:

// New macro that includes severity, filename and line number
#define CUSTOM_LOG(logger, sev) \
   BOOST_LOG_STREAM_WITH_PARAMS( \
      (logger), \
         (set_get_attrib("File", path_to_filename(__FILE__))) \
         (set_get_attrib("Line", __LINE__)) \
         (::boost::log::keywords::severity = (boost::log::trivial::sev)) \
   )

// Set attribute and return the new value
template<typename ValueType>
ValueType set_get_attrib(const char* name, ValueType value) {
   auto attr = logging::attribute_cast<attrs::mutable_constant<ValueType>>(logging::core::get()->get_global_attributes()[name]);
   attr.set(value);
   return attr.get();
}

// Convert file path to only the filename
std::string path_to_filename(std::string path) {
   return path.substr(path.find_last_of("/\\")+1);
}

The next complete source code create two sinks. The first uses File and Line attributes, the second not.

#include <boost/log/trivial.hpp>
#include <boost/log/sources/severity_logger.hpp>
#include <boost/log/utility/setup/file.hpp>
#include <boost/log/utility/setup/console.hpp>
#include <boost/log/expressions.hpp>
#include <boost/log/utility/setup/common_attributes.hpp>
#include <boost/log/attributes/mutable_constant.hpp>
#include <boost/date_time/posix_time/posix_time_types.hpp>
#include <boost/log/support/date_time.hpp>
#include <boost/log/attributes/mutable_constant.hpp>

namespace logging  = boost::log;
namespace attrs    = boost::log::attributes;
namespace expr     = boost::log::expressions;
namespace src      = boost::log::sources;
namespace keywords = boost::log::keywords;

// New macro that includes severity, filename and line number
#define CUSTOM_LOG(logger, sev) \
   BOOST_LOG_STREAM_WITH_PARAMS( \
      (logger), \
         (set_get_attrib("File", path_to_filename(__FILE__))) \
         (set_get_attrib("Line", __LINE__)) \
         (::boost::log::keywords::severity = (boost::log::trivial::sev)) \
   )

// Set attribute and return the new value
template<typename ValueType>
ValueType set_get_attrib(const char* name, ValueType value) {
   auto attr = logging::attribute_cast<attrs::mutable_constant<ValueType>>(logging::core::get()->get_global_attributes()[name]);
   attr.set(value);
   return attr.get();
}

// Convert file path to only the filename
std::string path_to_filename(std::string path) {
   return path.substr(path.find_last_of("/\\")+1);
}

void init() {
   // New attributes that hold filename and line number
   logging::core::get()->add_global_attribute("File", attrs::mutable_constant<std::string>(""));
   logging::core::get()->add_global_attribute("Line", attrs::mutable_constant<int>(0));

   // A file log with time, severity, filename, line and message
   logging::add_file_log (
    keywords::file_name = "sample.log",
    keywords::format = (
     expr::stream
      << expr::format_date_time<boost::posix_time::ptime>("TimeStamp", "%Y-%m-%d_%H:%M:%S.%f")
      << ": <" << boost::log::trivial::severity << "> "
      << '['   << expr::attr<std::string>("File")
               << ':' << expr::attr<int>("Line") << "] "
      << expr::smessage
    )
   );
   // A console log with only time and message
   logging::add_console_log (
    std::clog,
    keywords::format = (
     expr::stream
      << expr::format_date_time< boost::posix_time::ptime >("TimeStamp", "%Y-%m-%d %H:%M:%S")
      << " | " << expr::smessage
    )
   );
   logging::add_common_attributes();
}

int main(int argc, char* argv[]) {
   init();
   src::severity_logger<logging::trivial::severity_level> lg;

   CUSTOM_LOG(lg, debug) << "A regular message";
   return 0;
}

The statement CUSTOM_LOG(lg, debug) << "A regular message"; generates two outputs, writing a log file with this format...

2015-10-15_15:25:12.743153: <debug> [main.cpp:61] A regular message

...and outputs to the console this:

2015-10-15 16:58:35 | A regular message